Ezra 3:8

Now in the second year of their coming to the house of God at Jerusalem in the second month, Zerubbabel the son of Shealtiel and Jeshua the son of Jozadak and the rest of their brothers the priests and the Levites, and all who came from the captivity to Jerusalem, began the work and appointed the Levites from twenty years and older to oversee the work of the house of the Lord.

Numbers 4:3

from thirty years and upward, even to fifty years old, all who enter the service to do the work in the tent of meeting.

1 Chronicles 23:4

Of these, 24,000 were to oversee the work of the house of the Lord; and 6,000 were officers and judges,

1 Chronicles 23:24-32

These were the sons of Levi according to their fathers’ households, even the heads of the fathers’ households of those of them who were counted, in the number of names by their census, doing the work for the service of the house of the Lord, from twenty years old and upward.

Ezra 4:3

But Zerubbabel and Jeshua and the rest of the heads of fathers’ households of Israel said to them, “You have nothing in common with us in building a house to our God; but we ourselves will together build to the Lord God of Israel, as King Cyrus, the king of Persia has commanded us.”

Treasury of Scripture Knowledge

Summary

Now in the second year of their coming unto the house of God at Jerusalem, in the second month, began Zerubbabel the son of Shealtiel, and Jeshua the son of Jozadak, and the remnant of their brethren the priests and the Levites, and all they that were come out of the captivity unto Jerusalem; and appointed the Levites, from twenty years old and upward, to set forward the work of the house of the LORD.

Twenty years old

Bible References

Twenty years old

Numbers 4:3
from thirty years and upward, even to fifty years old, all who enter the service to do the work in the tent of meeting.
1 Chronicles 23:24
These were the sons of Levi according to their fathers’ households, even the heads of the fathers’ households of those of them who were counted, in the number of names by their census, doing the work for the service of the house of the Lord, from twenty years old and upward.